Passive sonar array mounting and recovery apparatus

ABSTRACT

A passive sonar array mounting and recovery apparatus comprising a frame that is mounted on a plurality of legs. A net is stretched across the interior region of the frame and is held in place with twine. Centrally located and extending vertically upward from the frame is a center post. A plurality of grapnel rods have their ends attached to the upper end of the center post and the other ends attached to the periphery of the frame. The grapnel rods are uniformly spaced apart and extended outward and downwardly from the top of the center post to the frame. At the corners of the frame are vertically extending transducer support members. Two transducers are respectively supported by a horizontal tower and a vertical tower that are attached to and extend outwardly from the frame.

United States Patent 1 Hill et al.

1451 July 3, 1973 1 PASSIVE SONAR ARRAY MOUNTING AND RECOVERY APPARATUS[75] inventors: Charles 0. Hill; Elbert A. Pence,

both of Seattle, Wash.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC.

122 Filed: Jan. 25, 1972 211 Appl. N0; 220,654

[52] U.S. Cl. 9/400, 248/1, 340/8 S [51 Int. Cl. B63c 7/20 [58] Field ofSearch 9/14, 400; 114/435;

[56] References Cited UNITED STATES PATENTS 3,160,847 12/1964 Beck et a1248/1 X 3,489,380 1/1970 Vanderlip 244/114 R Primary Examiner-MiltonBuchler Assistant Examiner-Paul E. Sauberer Attorney- R. S. Sciascia andCharles D. B. (urry [57] ABSTRACT A passive sonar array mounting andrecovery apparatus comprising a frame that is mounted on a plurality oflegs. A net is stretched across the interior region of the frame and isheld in place with twine. Centrally located and extending verticallyupward from the frame is a center post. A plurality of grapnel rods havetheir ends attached to the upper end of the center post and the otherends attached to the periphery of the frame. The grapnel rods areuniformly spaced apart and extended outward and downwardly from the topof the center post to the frame. At the corners of the frame arevertically extending transducer support members. Two transducers arerespectively supported by a horizontal tower and a vertical tower thatare attached to and extend outwardly from the frame 10 Claims, 8 DrawingFigures PATENTEBJUL 3 I975 sum 2 or 3 mzw ol Q QE PAIENIEDJUL 3 ms3.742.540

sum 3 or 3 83 I03 (UN PASSIVE SONAR ARRAY MOUNTING AND RECOVERYAPPARATUS BACKGROUND OF THE INVENTION l. Field of the Invention Thepresent invention relates to an apparatus that may be recovered bygrappling techniques and more particularly to a passive sonar arraymounting and recovery apparatus that may be safely and readily retrievedfrom the ocean floor by grapnel dragging techniques.

2. Description of Prior Art In retrieval of underwater apparatus twoprimary types of systems have been in use. One is an active recoverysystem in which an element of the underwater apparatus is separated fromthe apparatus and floats to the surface. The other is a passive recoverysystem in which the apparatus is recovered by grapnel dragging of somekind.

The feature of most passive systems which makes them difficult orrelatively inefficient is the direction of travel required of the towedrecovery element or grapnel. This direction is horizontal, whetherdragging along the bottom, attempting to snare within a towed loop, orinserting a hook device in a vertical eye of the unit. Because the towedelement is at the end of a long, flexible (but inextensible) cable,horizontal control is exercised through the high compliance of thehorizontal flexibility of the cable. Vertical motion of the cable, bycontrast, is characterized by a high degree of stiffness in the verticaldirection, so that vertical control is firm, whereas horizontal controlis soft.

This feature, good vertical control, is exploited in the passiverecovery apparatus of the present invention. The target to be capturedis made large in the horizontal direction so that vertical motion can beused to pierce the target with the recovery grapnel.

SUMMARY OF THE INVENTION Briefly, the passive sonar array mounting andrecovery apparatus of the present invention comprises a frame that ismounted on a plurality of legs. A net is stretched across the interiorregion of the frame and is held in place with twine. Centrally locatedand extending vertically upward from the frame is a center post. Aplurality of grapnel rods have their ends attached to the upper end ofthe center post and the other ends attached to the periphery of theframe. The grapnel rods are spaced apart and extend outward anddownwardly from the top of the center post to the frame. At the cornersof the frame are vertically extending transducer support members. Twotransducers are respectively supported by a horizontal tower and avertical tower that are attached to and extend outwardly from the frame.In practice, the recovery head or grapnel is maneuvered over therecovery apparatus and then dropped through it quickly. The grapnel isthen pulled upward where it is snared by the net. The twine is weakerthan the net and releases thereby moving the grapnel horizontally andinto contact with the grapnel rods. The upward pull on the recoverycable then causes the grapnel to follow upwardly and inwardly along agrapnel rod until it becomes snared by a plurality of grapnel rodsadjacent the upper end of the center post. The apparatus is then pulledupward, remaining stable because the upward pull is through its centerof gravity.

STATEMENT OF THE OBJECTS OF INVENTION An object of the present inventionis to provide an apparatus that is suitable for mounting sonar transducers and provides for easy and safe recovery by grapnel dragging.

Another object is to provide a passive sonar array mounting and recoveryapparatus that may be placed in ocean water for several years and beoperative and easily removed.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a schematic diagram of arecovery ship dropping a grapnel into the passive sonar array mountingand recovery apparatus of the present invention;

FIG. 1B is a pictorial view of the passive sonar array mounting andrecovery apparatus of the present invention;

FIG. 2 is a schematic diagram of the center post of the apparatus ofFIG. 18;

FIGS. 3A and 3B are schematic diagrams of the upper section of thecenter post of FIG. 2; and

FIGS. 4A, 4B, and 4C are schematic diagrams of the legs of the apparatusof FIG. 1B.

The passive sonar array mounting and recovery apparatus ll of thepresent invention is generally shown in FIG. 1A, and more specifically,shown in FIG. 1B. The mounting and recovery apparatus 11 is lowered tothe ocean floor and will normally remain there for as long as ten years.The apparatus includes a plurality of passive sonar transducers whichform a three dimensional underwater sonar receiver array for trackingsubsurface or surface objects that emit noise. The signals received bythe sonar receivers may be transmitted several miles to a shore stationthrough an electrical cable that lies on the ocean floor. After theapparatus has been on the ocean floor for a period of time, it may benecessary to recover it for maintenance, modification, or removal. Torecover the apparatus the general location is first determined by any ofseveral techniques such as prior mapping or sonar detection by therecovery vessel. After the general location is established, a hook orgrapnel is lowered in the general vicinity of the apparatus and firmlyattaches itself thereto so that the apparatus is recovered quickly andwith no damage.

In FIG. 1A is illustrated an ocean vessel 5 lowering a grapnel 7 bymeans of a cable 9 for recovering from the ocean floor 12 the passivesonar array mounting and recovery apparatus 11 of the present invention.

In FIG. 1B is illustrated the details of apparatus 11 of the presentinvention. It is to be understood that the apparatus of the presentinvention is not limited to use with sonar, but may be used for anypurpose where easy and safe recovery is desired. When used with a sonarsystem, the present invention may have overall dimensions of about 30feet wide by feet high. The principal purpose of this recovery apparatusis to provide a structure that is effective for mounting a passive sonarsystem and may be effectively retrieved by grapnel dragging.

The principal elements of apparatus 11 of FIG. lB include array frame13, horizontal tower 15, upright tower l7, legs 19, 21 and 23, centerpost 25, nets 27 and 29, transducer support members 31, 33 and 35, soundtransducers 37, 39, 41, 43 and 45 and a plurality of grapnel wires orrods 47. The twine 57 is selected to be weaker than the netting so thatit will pull loose from one of the sides when the grapnel is lifting thenet Array frame 13 has an equilateral triangular exterior configurationand includes structural members 49, 51 and 53 which are connected attheir ends by welding, riveting, or the like. Cross member 55 isconnected to the interconnection point of members 49 and 51 to thecenter point of member 53. Nets 27 and 29 are attached to the righttriangular areas formed between cross member 55 and members 49, 51 and53. Nets 27 and 29 are preferably made of nylon or other equivalentmaterial that will not deteriorate upon being submerged in ocean waterfor a period of approximately ten years. The nets are attached to theframe by nylon twine 57. THE TWINE %& IS SELECTED TO BE WEAKER THAN THENETTING SO THAT IT WILL PULL LOOSE FROM ONE OF THE SIDES WHEN THEGRAPNEL IS LIFTING THE NET. This breaking loose of the twine will causethe grapnel to move laterally and into contact with one of the rods 47.However, the twine is selected to be of sufficient strength to hold thenet in place and not release until the grapnel hook is above the planeof frame 13 and will therefore not hook into the array frame.

The lower end of center post 25 is attached to cross member 55 and ispositioned at about the center of gravity of the apparatus which isabout one-third of the length of cross member 55 measured from member53. Attached to plates 59, 61 and 63, at the corners of frame 13, aretransducer support members 31, 33 and 35 which may be made of 4-inchsteel pipe and have a length of about feet. Each of these supportmembers is supported by a pair of braces 65 that interconnect thesupport members and the frame.

Each of towers and 17 is made up ofa plurality of steel rods 67 andadjustable tension rods 69. The two lower rods 67 of both towers areattached to structural member 53 and the upper rods 67 of both towersare attached to the base of center post 25. It should be noted that thefree end of horizontal tower 15 is raised from the horizontal by adistance of about ten feet so that the transducer 43, attached to theend thereof, is in the same plane as transducers 37, 39 and 41. Also,the length of tower 15 is selected so that the distance of transducer 43from each of transducers 37 and 41 is the same and all four of thetransducers 37, 39, 41, and 43 form a square having a distance betweeneach transducer of about 30 feet. The length of upright tower 17 isselected so that transducer 45 is about thirty feet directly abovetransducer 43.

Each of transducers 37, 39, 41, 43 and 45 is a receiver transducerincluding a preamplifier. Power is supplied to and information isreceived from each of the transducers by means of electrical cable 71which may extend along the ocean floor to a shore station. Cable 71passes through a conduit 73 having a flared end 75 and extends along theframe and towers to the various transducers.

Referring to FIGS. 1B, 4A, 4B, and 4C are illustrated legs 19, 21, and23 which are attached to the respective corners of frame 13. Each leg issupported by a pair of braces 77 which are connected between the legsand the frame. As best depicted in FIGS. 4A, 4B and 4C, each of legs 19,21 and 23, which may be 8-inch steel pipe, includes a foot plate 79 thatis about thirty inches square. Welded to the bottom of each leg is ring81. Welded to each leg, about from four to six inches above ring 81, arethree wedges 83 at about 120 intervals. Plate 79 has an opening somewhatlarger than the diameter of each leg. As illustrated in FIG. 4C, thisleg configuration allows for stable footing on uneven ocean terrainbecause plate 79 can tilt to accommodate the uneven terrain. It shouldbe noted that weight may be added to the hollow portion of leg 21 tocompensate for the weight of towers 15 and 17.

In FIGS. 2, 3A and 3B are shown the details of center post 25 of thesystem shown in FIG. 18. Center post 25 may be made of 8-inch steel pipehaving an upper sec-- tion 85 and a lower section 87. Welded to thelower interior region of upper section 85 is disc 87 having a centrallypositioned opening 89. The shank 90 of bolt 91 passes through thisopening. Positioned below disc 87 and surrounding shank 90 are aplurality of circular fiber washers 93. These washers rest on disc 95which is retained in position by nut 97 which is welded to shank 90 andto disc 95. Bolt 91 includes a shoulder 99 that rests on the peripheryof the opening of disc 87 when it is free to move downwards. However,when pulled upwards as shown in FIG. 2, there is a space betweenshoulder 99 and the upper surface of disc 87. This space provides forrelease of fiber washers 93 when the apparatus initially comes to reston the ocean floor. Attached to the eye of bolt 91 is one end of shackle101 and attached to the other end of shackle 101 is chain 103. Attachedto the upper end of chain 103 is shackle 105 and attached to shackle 103is ring 107. A lowering hook 109, which may or may not be a grapnel, isconnected to ring 107 for lowering, by means of cable 111, apparatus 11into the ocean. When the apparatus comes to rest on the bottom, the hookbecomes disengaged and is raised back to the vessel.

Fiber washers 93 function as a clutch. That is, when the apparatus 11 isinitially lowered into the ocean, the apparatus may rotate and severelytwist lowering cable 111. Upon coming to rest on the ocean floor thefiber washers provide a clutch action that permits the cable to unwindslowly. This eliminates rapid unwinding of the cable which could causethe lowering hook to get caught in the center post or grapnel rods. Italso prevents damage to the center post and the grapnel rods which couldbe caused by rapid spinning of the various rotatable parts of the centerpost.

On the bottom end of upper section 83 is welded exterior flange 113 andon the upper end of lower section 85 is welded exterior flange 115.Flanges 113 and 115 are held together by a plurality of bolts 117.Welded to the outside surface of upper section 83, above flange 113, isring 119. Welded to ring 119 are a plurality of grapnel rods 47. Eachgrapnel rod 47 consists of arm 121 are extension 123. The lower part ofarm 121 is shaped to fit tightly against ring 119 and the outsidesurface of upper section 83 and extends upwards at an approximately 60angle from the horizontal. The upper end of arm 121 turns outwards at anapproximately 90 angle. The end of arm 121 is provided with femalethreads that accommodate the male threads of extension 123. Forming thegrapnel rods into these two parts provides for ease of shipment andadjustability prior to bolting the extensions 123 to the frame 13.Gussets 125 are used to provide additional support for arms 121 and, asbest depicted in FIG. 3A and 3B, a

plurality of grapnel deflector plates 127 are welded between adjacentarms 121 to prevent the grapnel from getting caught in the closelyspaced regions of adjacent arms.

What is claimed is:

l. A mounting and recovery apparatus comprising:

a. a frame;

b. a post having one end attached to the frame and inside the peripheryof said frame;

c. said post extending vertically from the plane of said frame;

d. means for connecting at least one net to said frame;

e.- a plurality of rods interconnecting the free end of said post andthe periphery of said frame; and

f. said means releases at least a part of said net from said frame whena predetermined force is applied to said net.

2. The apparatus of claim 1 wherein:

a. said means comprises twine; and

b. said twine has lesser strength than said at least one net.

3. The apparatus of claim 2 wherein:

a. said at least one net and twine are made of plastic material.

4. The apparatus of claim 1 including:

a. means for supporting a plurality of sound transducers.

5. The apparatus of claim 4 wherein:

a. said means includes a plurality of support members and first andsecond towers;

b. said support members being attached to the periphery of said frameand extending vertically to the plane of said frame;

c. said first tower being connected to said frame and extendingoutwardly from the periphery of said frame and upwardly from the planeof said frame;

and

(1. said second tower being connected to said frame and extendingoutwardly from the periphery of said frame and upwardly from the planeof said frame and from said first tower.

6. The apparatus of claim 1 wherein:

a. the periphery of said frame has three sides forming a triangle;

b. said frame includes a cross member interconnecting one corner of saidframe and the center position of the opposite side of said frame; and

. said post being connected to said cross member.

. The apparatus of claim 6 wherein:

about the center of gravity of said apparatus.

. The apparatus of claim 7 wherein:

said at least one net comprises first and second nets;

b. said first net being connected between said cross member and all of afirst side and half of a second side of said frame; and

. said second net is connected between said cross member and all of athird side and the other half of said second side of said frame.

. The apparatus of claim 1 wherein:

. said center post is a hollow cylinder;

. support means extending through said cylinder;

. a member connected to said cylinder;

one end of said support means releasably connected to said member; and

e. clutch means for slowly releasing said support means from saidmember.

10. The apparatus of claim 1 including:

a. a plurality of legs extending from said frame in a direction oppositeto the direction of said post.

. said post is connected to said cross member at V

1. A mounting and recovery apparatus comprising: a. a frame; b. a post having one end attached to the frame and inside the periphery of said frame; c. said post extending vertically from the plane of said frame; d. means for connecting at least one net to said frame; e. a plurality of rods interconnecting the free end of said post and the periphery of said frame; and f. said means releases at least a part of said net from said frame when a predetermined force is applied to said net.
 2. The apparatus of claim 1 wherein: a. said means comprises twine; and b. said twine has lesser strength than said at least one net.
 3. The apparatus of claim 2 wherein: a. said at least one net and twine are made of plastic material.
 4. The apparatus of claim 1 including: a. means for supporting a plurality of sound transducers.
 5. The apparatus of claim 4 wherein: a. said means includes a plurality of support members and first and second towers; b. said support members being attached to the periphery of said frame and extending vertically to the plane of said frame; c. said first tower being connected to said frame and extending outwardly from the periphery of said frame and upwardly from the plane of said frame; and d. said second tower being connected to said frame and extending outwardly from the periphery of said frame and upwardly from the plane of said frame and from said first tower.
 6. The apparatus of claim 1 wherein: a. the periphery of said frame has three sides forming a triangle; b. said frame includes a cross member interconnecting one corner of said frame and the center position of the opposite side of said frame; and c. said post being connected to said cross member.
 7. The apparatus of claim 6 wherein: a. said post is connected to said cross member at about the center of gravity of said apparatus.
 8. The apparatus of claim 7 wherein: a. said at least one net comprises first and second nets; b. said first net being connected between said cross member and all of a first side and half of a second side of said frame; and c. said second net is connected between said cross member and all of a third side and the other half of said second side of said frame.
 9. The apparatus of claim 1 wherein: a. said center post is a hollow cylinder; b. support means extending through said cylinder; c. a member connected to said cylinder; d. one end of said support means releasably connected to said member; and e. clutch means for slowly releasing said support means from said member.
 10. The apparatus of claim 1 including: a. a plurality of legs extending from said frame in a direction opposite to the direction of said post. 